McClaren admits now Al Nassr star Ronaldo's unwillingness to work and press off the ball ultimately saw him and then manager Erik ten Hag fall out.
Speaking on The Good, The Bad and The Football podcast, McClaren said: "There was a lot of battles on that training field.
"There was a lot of 'all I want you to do is this, this, this and this'. That was Erik's coaching - Ronnie this is your job.
"I used to say to Ronnie, 'all he wants you to do is, you're the first press, make one run, make two runs, and maybe make a third one, if you feel like it. And then, recover back into the middle, in case we win the ball, and then we can play to you. That's all he wants you to do.
"If you can't do that, you won't be playing. Or if you won't do that, you can't be playing. Okay, or he won't pick you. I'm telling you, he won't pick you.
"It's not like, I think other people would, and that's the difference, other people would. But Erik was, no, I'm doing that, and he's got to do it, otherwise he doesn't play.
"It was a little bit of a fight. Not a fight, but a standoff, and who is going to win? Erik stuck to his guns. I think most managers would accommodate to that. some managers are like that. But he stuck to his guns."